Ambiente sedimentario de depositación de las calizas de la formación San Eduardo (EOCENO medio), Recinto San Antonio, cantón Playas, provincia del Guayas.
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2020-04
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Facultad de Ciencias Naturales, Universidad de Guayaquil
Resumen
La formación San Eduardo (Eoceno Temprano- Ecoceno Medio) consiste de calizas compactas, chert, turbiditas bien estratificadas (calcarenitas y calciduritas); compuesta de fragmentos y granos de arrecifes de algas, intra estratificadas con menores lutitas y cherts; sobreyace a la formación Guayaquil (Cretácico) y subyace a la formación las Delicias (Eoceno Tardío). Las calizas sonutilizadas principalmente en la industria de la construcción. el objetivo de este estudio es definir la composición, edad y ambiente sedimentario deposicional de las calizas de la formación San Eduardo 1,2,y 3; son rocas calizas compactas, calizas meteorizadas y arcillolitas. Se analizaron nueve láminas delgadas. Se utilizaron la metodología de Dunham (1972) y Folk (1962) para clasificar las rocas carbonáticas; la clasificación de Wilson (1975) para identificar su ambiente de deposición; y análisis químico para la determinación del porcentaje de carbonato de calcio. Las rocas calizas tienen un promedio del 88% de carbonato de calcio, petrográficamente son wackestone (caliza lodosa), packstone (caliza granular lodosa) y lodolita calcárea. Para la caliza San Eduardo se identificó una edad Eoceno Medio, pisos Luteciense al Bartoniense, por el contenido de microorganismos bentónicos y planctónicos, macrofósiles, algas calcáreas y el hallazgo del foraminífero Chavigerinella eocanica. el ambiente sedimentario deposicional es de Plataforma de Laguna Abierta a Plataforma restringida.
The San Eduardo formation (Early Eocene - Middle Eocene) consists of compact limestones, chert, well-layered turbidites (calcarenites and calcidurites); composed of fragments and grains of algae reefs, intra stratified with minor shales and cherts; it overlies the Guayaquil formation (Cretácico) and underlies the Las Delicias formation (Late Eocene). Limestones are mainly used in the construction industry. The objetive of this study is to define the composition, age and depositional sedimetary environment of the San Eduardo 1, 2, and 3; with compact limestone rocks, weathered limestone and claystones. Nine thin sectios were analyzed. Dunham's (1972) and Folk's (1962) methodology was used to classify carbonate rocks; Wilson's classification (1975) to identify its depositional environemt, and chemical analysis to determie the percentage calcium carbonate. Limestone rocks have an average of 88% calcium carbonate, petrographically they are wackestones (muddy limestone), packstones (muddy granular limestone) and calcareous muldstones. For the San Eduardo limestone, a Middle Eocene age was identified, from the Lutecian to the Bartonian stages, due to the content of benthic and planktonic microorganisms, macrofossils, calcareous algae and the finding of the foraminera Clavigerinella eocanica. The depositional sedimentary environmeent is from the Open Lagoon Platform to a restricted Platform.
The San Eduardo formation (Early Eocene - Middle Eocene) consists of compact limestones, chert, well-layered turbidites (calcarenites and calcidurites); composed of fragments and grains of algae reefs, intra stratified with minor shales and cherts; it overlies the Guayaquil formation (Cretácico) and underlies the Las Delicias formation (Late Eocene). Limestones are mainly used in the construction industry. The objetive of this study is to define the composition, age and depositional sedimetary environment of the San Eduardo 1, 2, and 3; with compact limestone rocks, weathered limestone and claystones. Nine thin sectios were analyzed. Dunham's (1972) and Folk's (1962) methodology was used to classify carbonate rocks; Wilson's classification (1975) to identify its depositional environemt, and chemical analysis to determie the percentage calcium carbonate. Limestone rocks have an average of 88% calcium carbonate, petrographically they are wackestones (muddy limestone), packstones (muddy granular limestone) and calcareous muldstones. For the San Eduardo limestone, a Middle Eocene age was identified, from the Lutecian to the Bartonian stages, due to the content of benthic and planktonic microorganisms, macrofossils, calcareous algae and the finding of the foraminera Clavigerinella eocanica. The depositional sedimentary environmeent is from the Open Lagoon Platform to a restricted Platform.